Data storage devices employ rotating data storage media such as hard disk drives. In a hard drive, data is written to the disk medium using a write head which generates a high localized magnetic field which aligns magnetic domains within the disk in one of two directions. In some cases, the magnetization direction is up or down relative to the plane of the disk (perpendicular magnetic recording, or PMR). In other cases, the magnetization direction is within the plane of the disk. In all cases, this data may then be read-out with a read head. The write and read heads are typically integrated within a single assembly. To achieve steadily increasing data storage densities (typically measured in bits/inch2), which are now achieving levels near 1012 bits/in2, the sizes of magnetic regions storing individual bits have been reduced to nm levels.
To achieve these increasing data storage densities, the dimensions (widths) of data tracks are being steadily decreased and the track-to-track spacings also reduced correspondingly, with the result that magnetic interference effects between neighboring tracks (adjacent track interference, ATI), and nearby tracks (far track interference, FTI) are becoming an increasing problem for the maintenance of data integrity. The current solution to this problem is to monitor the total number of writes on any given track and in idle time (i.e., in periods during which the host computer is not transmitting read or write commands to the HDD), execute a background media scan. During the background media scan, lower levels for correction (i.e., fewer error-correction code bits) are used—if the track can be read but is compromised, it is refreshed (i.e., the same data is rewritten into that same physical location on the disk medium). The time required for these data readout and rewriting operations may affect the overall performance of the HDD and is undesirable.
Thus it would be advantageous in a data storage system to provide a method for improved control of ATI and FTI effects with reduced overhead on HDD operation, thereby improving the overall performance of the HDD.
It would also be advantageous to provide a method for avoiding ATI and FTI effects on data blocks, thereby reducing or eliminating the need to rewrite the same data into these data blocks, with the corresponding overhead on HDD operation.
A further advantage would be to provide a method for remapping logical block addresses (LBAs) from one physical data location to another physical data location to effect a reduction in “hot spots” on the disk storage medium at which very high and continuing rates of data writing are occurring.